Tiagra derailleur cheaper than chain... Odd...

I've been looking around at options for upgrading/repairing my old skool down-tube shifting RX-100 groupset, and a Tiagra setup (keeping the RX-100 front derailleur + brakes and the 105 chainrings I've got) seems to be a logical thing to do based on my meagre grad-student budget (and even this project may be a way off yet).

But the really curious thing is that the Tiagra RD, for which the best price I can find is £16.99, is cheaper than an appropriate chain - usually in the £20 range for something half-decent. Yeah, I know the STI levers do most of the work, and that work would run me £104.99 for the pair, but still; it's odd that something so fancy-looking as a derailleur would cost less than something so seemingly basic as a chain.

I'd need a new rear wheel as well, of course, as the current freewheel is a 7-speed, but that's sort of the point; the cones are all pitted and it's a vain quest to keep the thing true - - and I'd never find a decent 7-speed road wheel, so to get a new wheel I pretty much have to take it all up to 9-speed.

I think the RX100 quality-wise was probably between Tiagra and 105. For a rear derailleur I'd rather have the 105. With chains I think you generally get what you pay for. I understand the importance of sticking to your graduate school budget.

Even better, just use your old derailleur. It will work fine with newer shifters. Just a reminder, you'll also want to get cable stops that mount where your shifters used to be, plus new cables, a couple of ferrules, housing, bar tape, etc.

Not sure why a chain is more expensive than a RD. Maybe chains require tighter tolerances, better materials, or more manufacturing steps? As I've stood up to power across an intersection I often marvel that the thin little chain can take the multiplied torque I produce. And I'm really not that powerful -can't imagine what a pro sprinter puts out.

quote - I'd need a new rear wheel as well, of course, as the current freewheel is a 7-speed, but that's sort of the point; the cones are all pitted and it's a vain quest to keep the thing true - - and I'd never find a decent 7-speed road wheel, so to get a new wheel I pretty much have to take it all up to 9-speed.[/QUOTE]

why not buy some sora sti levers? they are available in 7 speed. You may find that you cannot fit a 9 speed rear wheel, as it may be too wide for your frames (rear spacing). The Tiagra/Sora shifters should work well with your existing derailleur.
Also, not that you can fit 8 and 7 speed cassettes on to a 9 speed wheel. You have to use a spacer for the 7 speed, but it works very well. Btw, for the price of the upgrade you mention, you could easily get a Campagnolo Xenon GROUP! Cheap wheelset (eg Vuelta) 60ukp. Xenon group 130 ukp = 190ukp to run 9 speed campagnolo, versus 110ukp for the Tiagra STI's alone....

Btw, for the price of the upgrade you mention, you could easily get a Campagnolo Xenon GROUP! Cheap wheelset (eg Vuelta) 60ukp. Xenon group 130 ukp = 190ukp to run 9 speed campagnolo, versus 110ukp for the Tiagra STI's alone....

True... Though would a Xenon set be necessarily that much better than 15-year-old RX-100? And With Xenon levers I assume I'd have to go with Campy derailleurs - I'd more likely to for Sora levers and keep the existing derailleurs. But I don't like the thumb clicky things for shifting, so that's why I've been looking at Tiagra.

Ribble are selling off the Ultegra level 8 speed levers for about the same price as sora sti's. That would be a great option. 8 speed chains and cassettes are reckoned to be more durable than 9, and they are cheaper to boot.
The Xenon group option at 130ukp would include the derailleurs. You are right in thinking that things would work better with the campagnolo mechs.
To be honest, i doubt that tiagra would be much better than 15 year old rx-100 if it is in good nick. The biggest shifting improvement would probably come from some snazzy cables, well set up. I quite like the sora thumb shifters, but those of campagnolo levers are better placed. I find them tricky to use from the drops, but I don't ride there much. For me, it is worth it to have solid brake levers (which is why the bike i am riding right now has shimano downtube levers and exage brake levers).
dave

Are you sure you can't find a chain for less than 20 UKP? If you don't have a 10 spd. setup, you can find chains which are pretty cheap. I have an older 7 speed bike and bought an SRAM PC-58 here in the states for around $15 (at an online discounter). KMC also makes some pretty inexpensive chains that are of good quality.

What sort of width in the frame would I need to make sure an 8/9 speed wheel would fit??

130mm, as already pointed out. If you have a 126 mm steel frame, you can spread it safely or have a shop do this (that means you permanently bend it out to 130 mm). If you have an aluminum frame, it isn't safe to permanently deform the frame, but many people have good luck with squeezing the dropouts open a little bit to fit in a wider wheel.

I've been doing that for 1 year+ on my 1990 Trek 1100 aluminum frame, and it works great. I was worried about this at first, so I asked about rec.bicycles.tech and it turns out there are dozens of people doing this with no issues, some with thousands of miles on it.

The question though: If I spend the money on a wheel, STI shifters, new cassette, and rear derailleur, it'd be probably half or two-thirds the price of a used but good condition Tiagra or 105-equipped bike... Hmmm.... things to ponder. And thanks to Acorn_user for the Ribble suggestion. Nice prices there. I could get a pair of Tiagra wheels for £50.

Ah, good, well I measured it and it's 126, but out of curiosity pulled the rear wheel of a former housemate's semi-derilict Trek 1000, measured his, it's 130cm, and had a go putting his wheel on my bike. It really didn't take much effort to get the wheel to go on and it spun fine. So that's quite good news. I may pick up a pair of Tiagra wheels or see if I can track town a good price on just a rear Aksium wheel. Where can I find these spacers?

Tragically I got dirty chain grease all over one of my fairly-nice shirts. Suggestions?

I also noticed that my Reynolds531 steel Peugeot isn't really much heavier than the aluminium Trek 1000.

How likely am I to be able to get the 7-speed cassette w/ spacer to line up just where the old wheel did such that I can swap the two back and forth at will (such that I could use the old wheel for commuting and the new one for proper rides)?

The best spacers are dead cogs out of old cassettes, because they are free.
I went to a shop to do that to my new rear wheel last week, and they had used up all their cogs making decorations, so we used some bottom bracket spacers. Seems to work ok too, but without the Heath-Robinson element I liked.

I don't know about the wheel-changey thing- remember 8 speeds onto an old 7 speed hub won't work too well unless you can hash it.

Also, the Tiagra wheels are supercheap, but have you considered hand mades from Ribble, or Dave Hinde (both don't have great customer service reputations), or Chain Reaction cycles? A Sora hub with a Mavic MA3 rim would be cheap and stronger to boot! Also, M:Wheels do a pre-built version of the same; my experience of a similar wheel was great (until it was knicked)
Dave

How likely am I to be able to get the 7-speed cassette w/ spacer to line up just where the old wheel did such that I can swap the two back and forth at will (such that I could use the old wheel for commuting and the new one for proper rides)?

I'd say pretty likely, if you play around with different thin spacers and get it just right. I suspect, however, that you'll decide to use the new wheels all the time